Magnetoresistive sensors typically comprise a magnetization free layer and a magnetization fixed layer (pinned layer). The free layer is responsive to a magnetic field that is produced as a signal from a magnetic medium. The electrical resistance of the sensor depends on the angle between free layer and the pinned layer. Therefore, the resistance is varied according to the angle between the free layer and the pinned layer. The electrical resistance is read as a signal. When the magnetization free layer moves irregularly with respect to the signal magnetic field there will be noise or a sensing failure, and the reliability of the sensing device is decreased. In some devices, the magnetization free layer may be stabilized using a magnetic-domain-control field which is generated by a magnetic-domain-control film comprising a hard magnetic material. The hard magnetic material may be an alloy comprising Co or Fe, or an alloy thereof, along with Pt.
However, the magnetic charge at the ends of the magnetic-domain-control film generates the magnetic-domain-control field for stabilizing the free layer, on the other hand, so a large opposing magnetic field may be generated in the magnetic-domain-control film itself. This may result in the magnetization at the ends of the magnetic-domain-control film to be unstable, and the magnetization at the ends may cause an unstable magnetization. If demagnetization occurs after the magnetoresistive device has been shipped, there is a risk that the device may experience a malfunction. Therefore, there is a need to provide further stabilization in the magnetic-domain-control film in order to lessen the effect of the magnetic charge at the ends of the magnetic-domain-control film.
The problem of instability in conventional magnetic-domain-control films is due to the charge at the ends of the magnetic-domain-control film. The shape of current magnetic-domain-control films in the region of the element is a right-angle on the air bearing surface (ABS) side and a side opposite the ABS side, and the magnetic charge readily accumulates in the corners on the ABS side and the opposite side. Furthermore, the corners at the ends of the magnetic-domain-control film on the ABS side and the opposite side are also regions where there should be nucleation sites for magneto-switching, and there is a strong effect from the demagnetizing field.
It has been difficult to lessen the effect of the magnetic charge which accumulates in the corners in conventional magnetic-domain-control films. Accordingly, it would be beneficial to have a more stable magnetic-domain-control film which restricts magnetic charge accumulation in the corners at the ends of the magnetic-domain-control film on the ABS side and the opposite side.